System and head for continuously manufacturing composite structure

ABSTRACT

A system is disclosed for additively manufacturing a composite structure. The system may include a support, and a print head connected to and moveable by the support in multiple dimensions. The system may also include a cure enhancer mounted to the print head and configured to expose composite material discharging from the print head to energy, and a curing tool mounted to the print head downstream of the cure enhancer. The curing tool may be configured to expose the composite material to additional energy.

RELATED APPLICATIONS

This application is based on and claims the benefit of priority from U.S. Provisional Application No. 62/730,541 that was filed on Sep. 13, 2018, the contents of which are expressly incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to a manufacturing system and, more particularly, to a system and head for continuously manufacturing composite structures.

BACKGROUND

Continuous fiber 3D printing (a.k.a., CF3D®) involves the use of continuous fibers embedded within a matrix discharging from a moveable print head. The matrix can be a traditional thermoplastic, a powdered metal, a liquid resin (e.g., a UV curable and/or two-part resin), or a combination of any of these and other known matrixes. Upon exiting the print head, a head-mounted cure enhancer (e.g., a UV light, an ultrasonic emitter, a heat source, a catalyst supply, etc.) is activated to initiate and/or complete curing of the matrix. This curing occurs almost immediately, allowing for unsupported structures to be fabricated in free space. When fibers, particularly continuous fibers, are embedded within the structure, a strength of the structure may be multiplied beyond the matrix-dependent strength. An example of this technology is disclosed in U.S. Pat. 9,511,543 that issued to Tyler on Dec. 6, 2016 (“the '543 patent”).

Although CF3D® provides for increased strength, compared to manufacturing processes that do not utilize continuous fiber reinforcement, improvements can be made to the structure and/or operation of existing systems. The disclosed additive manufacturing system is uniquely configured to provide these improvements and/or to address other issues of the prior art.

SUMMARY

In one aspect, the present disclosure is directed to an additive manufacturing system. The additive manufacturing system may include a support, and a print head connected to and moveable by the support in multiple dimensions. The system may also include a cure enhancer mounted to the print head and configured to expose composite material discharging from the print head to energy, and a curing tool mounted to the print head downstream of the cure enhancer. The curing tool may be configured to expose the composite material to additional energy.

In another aspect, the present disclosure is directed to a method for additively manufacturing a composite structure. The method may include discharging from a print head a composite material, and moving in multiple dimensions the print head during discharging of the composite material. The method may also include exposing the composite material discharging from the print head to cure energy at a first location downstream of the print head, and exposing the composite material to additional energy at a second location further downstream of the print head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric illustration of an exemplary disclosed additive manufacturing system; and

FIG. 2 is a diagrammatic illustration of an exemplary print head that may be utilized with the system of FIG. 1; and

FIGS. 3, 4, and 5 are diagrammatic illustrations of various cure arrangements that may be utilized with the print head of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary system 10, which may be used to manufacture a composite structure 12 having any desired cross-sectional shape (e.g., ellipsoidal, polygonal, etc.). System 10 may include at least a moveable support 14 and a print head (“head”) 16. Head 16 may be coupled to and moved by support 14. In the disclosed embodiment of FIG. 1, support 14 is a robotic arm capable of moving head 16 in multiple directions during fabrication of structure 12, such that a resulting longitudinal axis of structure 12 is three-dimensional. It is contemplated, however, that support 14 could alternatively be an overhead gantry, a hybrid gantry/arm, or another type of movement system that is capable of moving head 16 in multiple directions during fabrication of structure 12. Although support 14 is shown as being capable of multi-axis (e.g., six or more axes) movement, it is contemplated that any other type of support 14 capable of moving head 16 in the same or in a different manner could also be utilized, if desired. In some embodiments, a drive may mechanically couple head 16 to support 14 and may include components that cooperate to move and/or supply power or materials to head 16.

Head 16 may be configured to receive or otherwise contain a matrix. The matrix may include any type of material (e.g., a liquid resin, such as a zero-volatile organic compound resin; a powdered metal; a solid filament, etc.) that is curable. Exemplary matrixes include thermosets, single- or multi-part epoxy resins, polyester resins, cationic epoxies, acrylated epoxies, urethanes, esters, thermoplastics, photopolymers, polyepoxides, thiols, alkenes, thiol-enes, reversible resins (e.g., Triazolinedione, a covalent-adaptable network, a spatioselective reversible resin, etc.) and more. In one embodiment, the matrix inside head 16 may be pressurized, for example by an external device (e.g., an extruder or another type of pump—not shown) that is fluidly connected to head 16 via a corresponding conduit (not shown). In another embodiment, however, the matrix pressure may be generated completely inside of head 16 by a similar type of device. In yet other embodiments, the matrix may be gravity-fed through and/or mixed within head 16. In some instances, the matrix inside head 16 may need to be kept cool and/or dark to inhibit premature curing; while in other instances, the matrix may need to be kept warm for similar reasons. In either situation, head 16 may be specially configured (e.g., insulated, temperature-controlled, shielded, etc.) to provide for these needs.

The matrix may be used to coat, encase, or otherwise at least partially surround or saturate (e.g., wet) any number of continuous reinforcements (e.g., separate fibers, tows, rovings, ribbons, and/or sheets of material) and, together with the reinforcements, make up at least a portion (e.g., a wall) of composite structure 12. The reinforcements may be stored within (e.g., on separate internal spools—not shown) or otherwise passed through head 16 (e.g., fed from one or more external spools—not shown). When multiple reinforcements are simultaneously used, the reinforcements may be of the same type and have the same diameter and cross-sectional shape (e.g., circular, square, flat, hollow, solid, etc.), or of a different type with different diameters and/or cross-sectional shapes. The reinforcements may include, for example, carbon fibers, vegetable fibers, wood fibers, mineral fibers, glass fibers, metallic wires, optical tubes, etc. It should be noted that the term “reinforcement” is meant to encompass both structural and non-structural types of continuous materials that can be at least partially encased in the matrix discharging from head 16.

The reinforcements may be exposed to (e.g., coated with) the matrix while the reinforcements are inside head 16, while the reinforcements are being passed to head 16 (e.g., as a prepreg material), and/or while the reinforcements are discharging from head 16, as desired. The matrix, dry reinforcements, and/or reinforcements that are already exposed to the matrix (e.g., wetted reinforcements) may be transported into head 16 in any manner apparent to one skilled in the art.

The matrix and reinforcement may be discharged from head 16 via at least two different modes of operation. In a first mode of operation, the matrix and reinforcement are extruded (e.g., pushed under pressure and/or mechanical force) from head 16, as head 16 is moved by support 14 to create the 3-dimensional shape of structure 12. In a second mode of operation, at least the reinforcement is pulled from head 16, such that a tensile stress is created in the reinforcement during discharge. In this mode of operation, the matrix may cling to the reinforcement and thereby also be pulled from head 16 along with the reinforcement, and/or the matrix may be discharged from head 16 under pressure along with the pulled reinforcement. In the second mode of operation, where the matrix material is being pulled from head 16 with the reinforcement, the resulting tension in the reinforcement may increase a strength of structure 12 (e.g., by aligning the reinforcements, inhibiting buckling, equally distributing loads, etc.), while also allowing for a greater length of unsupported structure 12 to have a straighter trajectory (e.g., by creating moments that oppose gravity).

The reinforcement may be pulled from head 16 as a result of head 16 moving away from an anchor point 18. In particular, at the start of structure-formation, a length of matrix-impregnated reinforcement may be pulled and/or pushed from head 16, deposited onto a stationary or moveable anchor point 18, and cured, such that the discharged material adheres to anchor point 18. Thereafter, head 16 may be moved away from anchor point 18, and the relative movement may cause additional reinforcement to be pulled from head 16. It should be noted that the movement of the reinforcement through head 16 could be assisted (e.g., via internal feed mechanisms), if desired. However, the discharge rate of the reinforcement from head 16 may primarily be the result of relative movement between head 16 and anchor point 18, such that tension is created within the reinforcement.

Any number of reinforcements (represented as “R”) may be passed axially through head 16 and be discharged together with at least a partial coating of matrix (matrix represented as “M” in FIG. 2). At discharge (or shortly thereafter), one or more cure enhancers (e.g., one or more light sources, ultrasonic emitters, lasers, heaters, catalyst dispensers, microwave generators, etc.) 20 may expose the matrix coating to a cure energy (e.g., light energy, electromagnetic radiation, vibrations, heat, a chemical catalyst or hardener, etc.). The cure energy may trigger a chemical reaction, increase a rate of chemical reaction already occurring within the matrix, sinter the material, harden the material, or otherwise cause the material to cure as it discharges from head 16.

In some applications, higher levels of interlaminar strength, increased fiber volume, and/or decreased void content may be realized by pressing newly discharging material against underlying layers of material that were discharged during previous fabrication passes of head 16, before, after, and/or while the newly discharged material is exposed to the energy from cure enhancers 20. This pressing action may be facilitated by a rolling or sliding compactor 24 located at the discharge end of head 16. Exemplary compactors 24 are illustrated in FIGS. 2 (e.g., a rolling compactor) and 3-5 (e.g., a sliding compactor). Compactor 24 may embody any type of device known in the art for compressing the composite material discharging from a nozzle 26 of head 16 and/or for pressing the material against a previously discharged layer of material. In the depicted example, compactor 24 embodies a roller that is biased (e.g., via a spring 28) away from head 16 and toward the discharging material. It is contemplated, however, that a shoe-type compactor, a skirt-type compactor, or another type of compactor could alternatively or additionally be utilized. Compactor 24 may be location- and/or pressure-adjustable.

A controller 22 may be provided and communicatively coupled with support 14, head 16, any number and type of cure enhancers 20, and/or compactor 24. Controller 22 may embody a single processor or multiple processors that include a means for controlling an operation of system 10. Controller 22 may include one or more general- or special-purpose processors or microprocessors. Controller 22 may further include or be associated with a memory for storing data such as, for example, design limits, performance characteristics, operational instructions, matrix characteristics, reinforcement characteristics, characteristics of structure 12, and corresponding parameters of each component of system 10. Various other known circuits may be associated with controller 22, including power supply circuitry, signal-conditioning circuitry, solenoid/motor driver circuitry, communication circuitry, and other appropriate circuitry. Moreover, controller 22 may be capable of communicating with other components of system 10 via wired and/or wireless transmission.

One or more maps may be stored in the memory of controller 22 and used during fabrication of structure 12. Each of these maps may include a collection of data in the form of models, lookup tables, graphs, and/or equations. In the disclosed embodiment, the maps are used by controller 22 to determine desired characteristics of cure enhancers 20, the associated matrix, and/or the associated reinforcements at different locations within structure 12. The characteristics may include, among others, a type, quantity, and/or configuration of reinforcement and/or matrix to be discharged at a particular location within structure 12, and/or an amount, intensity, shape, and/or location of desired curing and/or compacting. Controller 22 may then correlate operation of support 14 (e.g., the location and/or orientation of head 16) and/or the discharge of material from head 16 (a type of material, desired performance of the material, cross-linking requirements of the material, a discharge rate, etc.) with the operation of cure enhancers 20 and compactor 24, such that structure 12 is produced in a desired manner.

In some applications, the composite material may only be partially cured by one or more cure enhancers 20, such that a desired shape and/or position of the composite material is temporarily maintained. In these applications, the curing initiated by cure enhancer(s) 20 may only be surface-deep. In order to provide a more thorough, deeper, and/or longer-lasting cure, an additional curing tool 30 may be beneficial. FIGS. 3-5 illustrate different arrangements of curing tool 30 relative to cure enhancer 20, compactor 24, and nozzle 26.

As shown in FIG. 3, curing tool 30 may be mounted to head 16 and generate a different type of cure energy than cure enhancer 20. For example, cure enhancer 20 is a UV light source in the embodiment of FIG. 3, while curing tool 30 is an electron beam generator. As an electron beam generator, curing tool 30 may be configured to generate a beam, line, or field of energy directed into and/or through the composite material being discharged by nozzle 26. The electron beam, line, and/or field generated by curing tool 30 may pass into and/or through the discharging material more readily than light and/or heat, making it ideal for large diameter discharge and/or material that blocks light (e.g., opaque material such as carbon fibers) and/or heat.

In the configuration of FIG. 3, curing tool 30 trails behind nozzle 26 and cure enhancer 20, but leads compactor 24. In order to help ensure that the energy from curing tool 30 is properly absorbed by the composite material, while also allowing head 16 to follow a complex trajectory, curing tool 30 may be pivotally connected to head 16 via one or more (e.g., two axially separated) hinges 32. Hinges 32 may allow head 16 to turn from a first trajectory to a second trajectory, while curing tool 30 continues to follow the first trajectory for a desired period of time. It is contemplated that an actuator (not show) could be associated with hinges 32 to affect selective pivoting of hinges 32, if desired. It is also contemplated that hinges 32 could be replaced with stationary brackets (not shown).

In the embodiment of FIG. 3, curing tool 30 may be positioned to ride just above an outer surface of the discharging material (e.g., within an offset distance that is about equal to or less than a diameter of the discharging material). This may help to ensure focus and efficient use of the energy from curing tool 30 into only the discharging material or into both the discharging material and a relatively small area surrounding the material. In addition, the location of curing tool 30 just above the surface of the discharging material may provide stable support for compactor 24, which may be connected to head 16 via curing tool 30.

As shown in FIG. 4, it may be beneficial in some applications to position compactor 24 between cure enhancer 20 and curing tool 30. In this position, compactor 24 may be able to exert pressure on the discharging material while the material is still in a relatively plastic phase. That is, more manipulation of the material may be possible prior to exposure to the energy from curing tool 30. In this embodiment, compactor 24 may be connected directly (i.e., not through curing tool 30) to head 16.

In addition, curing tool 30 may be spaced away from the discharging material by a greater distance (i.e., a distance greater than a diameter of the discharging material), as shown in FIG. 4. This may allow for some dissipation of the energy from curing tool 30 to a greater area surrounding the discharging material, which may help to ensure deeper and/or more thorough curing of structure 12.

In some situations, it may be beneficial to at least partially compact the discharging material prior to any energy exposure from cure enhancer 20 and/or curing tool 30. For this purpose, compactor 24 may be located downstream of nozzle 26 (e.g., immediately adjacent nozzle 26), but upstream of cure enhancer 20 and curing tool 30. This configuration is illustrated in FIG. 5. The discharging material may be more pliable at this point in time and location, enabling greater compaction and/or greater control over compaction. However, care should be taken to avoid excessive buildup of matrix (e.g., uncured, partially cured, and/or fully cured matrix) on compactor 24.

As also shown in FIG. 5, it may be possible to mount cure enhancer 20 to hinge(s) 32, if desired. In this example, it may be beneficial to extend the source location of cure energy toward the discharging material surface (e.g., via a light pipe 34 or other offset pipe), such that the amount of energy absorbed by the discharging material is sufficient to at least partially cure at least an outer surface of the material.

INDUSTRIAL APPLICABILITY

The disclosed systems may be used to continuously manufacture composite structures having any desired cross-sectional shape and length. The composite structures may include any number of different fibers of the same or different types and of the same or different diameters, and any number of different matrixes of the same or different makeup. Operation of system 10 will now be described in detail.

At a start of a manufacturing event, information regarding a desired structure 12 may be loaded into system 10 (e.g., into controller 22 that is responsible for regulating operations of support 14 and/or head 16). This information may include, among other things, a size (e.g., diameter, wall thickness, length, etc.), a contour (e.g., a trajectory), surface features (e.g., ridge size, location, thickness, length; flange size, location, thickness, length; etc.), connection geometry (e.g., locations and sizes of couplings, tees, splices, etc.), desired weave patterns, weave transition locations, etc. It should be noted that this information may alternatively or additionally be loaded into system 10 at different times and/or continuously during the manufacturing event, if desired. Based on the component information, one or more different reinforcements and/or matrix materials may be selectively installed and/or continuously supplied into system 10.

To install the reinforcements, individual fibers, tows, and/or ribbons may be passed through head 16. In some embodiments, the reinforcements may be passed under compactor 24 and/or attached to anchor point 18. Installation of the matrix material may include filling head 16 and/or coupling of an extruder (not shown) to head 16.

The component information may then be used to control operation of system 10. For example, the reinforcements may be pulled and/or pushed along with the matrix material from head 16. Support 14 may also selectively move head 16 and/or the anchor point in a desired manner, such that an axis of the resulting structure 12 follows a desired three-dimensional trajectory. Once structure 12 has grown to a desired length, structure 12 may be severed from system 10.

The disclosed head 16 may have improved curing and discharge-location control. Curing may be improved via precise control over the location(s) at which a desired amount and intensity of cure energy impinges discharging material. Discharge-location control may improve curing, such that the discharging material does not move significantly after compactor 24 has moved over the material.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed system and head. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system and head. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A system for manufacturing of a composite structure, comprising: a support; a print head connected to and moveable by the support in multiple dimensions; a cure enhancer mounted to the print head and configured to expose composite material discharging from the print head to cure energy; and a curing tool mounted to the print head downstream of the cure enhancer, the curing tool configured to expose the composite material to additional energy.
 2. The system of claim 1, wherein the cure enhancer is configured to generate a different type of cure energy than the cure energy generated by the curing tool.
 3. The system of claim 2, wherein: the cure enhancer is configured to generate at least one of light and heat; and the curing tool is configured to generate an electron beam.
 4. The system of claim 3, wherein the cure enhancer is configured to generate UV light.
 5. The system of claim 1, wherein the curing tool is pivotally connected to the print head.
 6. The system of claim 5, further including at least one hinge pivotally connected the curing tool to the print head.
 7. The system of claim 6, wherein the cure enhancer is mounted to the at least one hinge.
 8. The system of claim 1, further including a compactor connected to the print head and configured to compact the composite material discharging from the print head.
 9. The system of claim 8, wherein the compactor is connected to the print head at a location upstream of the cure enhancer and the curing tool.
 10. The system of claim 8, wherein the compactor is connected to the print head at a location downstream of the cure enhancer and the curing tool.
 11. The system of claim 8, wherein the compactor is connected to the print head at a location between the cure enhancer and the curing tool.
 12. The system of claim 1, wherein the curing tool is spaced away from the composite material discharging from the print head by a distance less than a diameter of the composite material.
 13. The system of claim 1, further including a light pipe extending from the cure enhancer toward the composite material discharging from the print head.
 14. The system of claim 1, further including a controller configured to coordinate operations of the support, the cure enhancer, and the curing tool.
 15. The system of claim 1, wherein: the cure enhancer is configured to facilitate surface-deep curing of the composite material discharging from the print head; and the curing tool is configured to facilitate through-curing of the composite material discharging from the print head.
 16. A system for manufacturing of a composite structure, comprising: a support; a print head connected to and moveable by the support in multiple dimensions; a compactor connected to the print head and configured to compact composite material discharging from the print head; a UV light mounted to the print head and configured to expose the composite material discharging from the print head to energy to facilitate surface-deep curing of the composite material; and an electron beam generator mounted to the print head downstream of the UV light, the electron beam generator configured to expose the composite material discharging to the print head to additional energy to facilitate through-curing of the composite material.
 17. A method of additively manufacturing a composite structure, comprising: discharging from a print head a composite material; moving in multiple dimensions the print head during discharging of the composite material; exposing the composite material discharging from the print head to cure energy at a first location downstream of the print head; and exposing the composite material to additional energy at a second location further downstream of the print head.
 18. The method of claim 17, wherein the cure energy is a different type of energy than the additional energy.
 19. The method of claim 18, wherein: the cure energy is at least one of light and heat and configured to facilitate surface-deep curing of the composite material discharging from the print head; and the additional energy an electron beam and configured to facilitate through-curing of the composite material discharging from the print head.
 20. The method of claim 17, further including compacting the composite material discharging from the print head while the composite material is still in a plastic phase. 